Ariel Sharon was a bulldog and a badger when it came to fighting. I'm no fan of the man, but when it came to war--and war is of utmost brutality--he was the most brutal. He was a terrible human being and a bad leader, but he was great at going to war.
Yes, I think that he was a better military leader that a politician. He was very smart in the acts of war, and how to effectively command troops into battle, in a way that would make a victory easier with out depending to heavily on the troops out muscleing the other side.
Ariel Sharon did a lot in order to make sure Israel was safe and made sure that it did not matter what personal opinion meant. He made a lot of controversial decisions in order to make living in Israel easier for everyone involved. This means great decisions both from a military and a political standpoint.
I think that while he was a military leader, he did quite well. He built the Israeli military up from nothing. Israel is now feared throughout the region due to its savvy and skilled military leaders that stay sharp due to constant conflict in Gaza. Israel also evolved into a political powerhouse of the region in spite of huge opposition. It becomes much more difficult to measure a political career as it has no true definition of victory or defeat. It is not as "zero-sum" as the military.
Ariel Sharon was a good military leader for Israel in times of crises and the camp massacres in Lebanon that occurred while he was on watch left a negative taste in the mouths of many. As Prime Minister, Sharon's development of a middle party, push for freer economic policies domestically, and his unilateral withdrawal from Gaza are all going to be recalled as successes for the State of Israel.